Obesity: Pre-programmed or Influenced?

A study by the University College London claims that obesity in children is likely to be highly influenced by their genes. Their study revealed that Body Mass Index (BMI) rates, and thus obesity, can be 77% based on our genetics. Although the study states that the chances of somebody being obese can be partially predetermined by their genes, a balanced diet and regular exercise are important in maintaining a healthy life-style regardless of one's BMI rate. (BMI can be calculated here)

Twins reared together are effective in studying the relationship between genes versus environment on obesity because they have the same genetic make-up and are generally exposed to similar diets. The results from these studies have showed that although obesity is influenced by environment and eating habits, it is largely affected by a person's genes. Professor Jane Wardle, who led the study, emphasized that "These results do not mean that a child with a high complement of susceptibility genes will inevitably become overweight, but that their genetic endowment gives them a stronger predisposition."  A child who is likely to have excessive weight gain due to their genes isn't indefinitely going to be obese; eating healthy and working hard to maintain a regular exercise schedule can help balance one's weight.

Twin studies have helped reveal the truth behind susceptibility of obesity, but naturally, there is still criticism regarding the credibility of these studies. Dr. Helen Wallace of GeneWatch UK stated that "It is impossible to draw reliable conclusions about the importance of genetic effects from twin data alone." Nevertheless, Wardle affirmed that "It is wrong to place all the blame for a child's excessive weight gain on the parents - it is more likely to be due to the child's genetic susceptibility." 

Obesity 'may be largely genetic'. (2008, February 7). Retrieved from http://news.bbc.co.uk/2/hi/7230065.stm  

Credibility of Twin Studies

Although geneticists realize the importance of twin studies in their field, many claim that not all experiments are reliable and credible. A large amount of geneticists claim that these studies are inefficient and the results, data, and information gathered from them must be utilized in a controlled manner. 

One of the issues geneticists face is the idea that if two people (or a pair of twins) spend hours together comparing their personalities, life stories, and the way they act, it not not unlikely that they would encounter many coincidental correspondences.  "If researchers created a control group of biologically unrelated pairs of the same age group, sex, and ethnicity who did not grow up together but who were as similar to one another in economic and cultural background as are separated twin pairs, wouldn't these pairs also exhibit striking similarities?" A reasonable response to this question would be that separated fraternal twins don't have as high of concordance rates as do separated identical twins. 

The answers to many questions such as these have been concluded from continual persistent research, but not all have been answered. As more research is done on said topic, more issues arise, such as the fact that most twins that have been studied and were reared apart have been reunited for several years before the research was done, thus influencing the credibility of the information gathered.  However, "twin studies illustrate why scientific thinking has shifted toward a greater appreciation of genetic influences."

Myers, D. G. (n.d.). Exploring psychology [pp. 66- 78]. Retrieved from http://books.google.com/books?id=bHvNT6qBtgYC&dq=twin+studies&source=gbs_navlinks_s

Alcohol Misuse Among Twins

So far we've seen that that personality, sexual orientation, or ideology are all influenced by genes; This has been showcased in the twin studies in which most twins all had similar physical attributes and character traits, unless they were reared apart and further influenced by differing environments and upbringings. However, I will introduce another trait that is fairly common among twins and thus affected by genes: alcohol misuse.

In recent studies, both female and male twins seemed to have high concordance rates on alcohol misuse- above 50%. Although studies are still hazy, there has been clear evidence that genes do play a major role in this subject. The risk for genetic influences to take effect on women regarding alcohol misuse can range from 50-61%. Curiously, the concordance rate tends to be lower among fraternal twins and be higher among identical twins. Enough being said, the similar genes in twins play a key role determining if they will begin misconduct with alcohol. Timothy J. Peters, author of Alcohol Misuse: A European Perspective states that "...genetic factors play a major role in the etiology of alcoholism in women."

Peters, T. J. (2005). Alcohol misuse: a european perspective [29-33]. (Adobe eReader Format), Retrieved from http://books.google.com/books?id=0vUcTbQlzk8C&printsec=copyright#v=onepage&q&f=false

Measuring Intelligence?

When conducting a twin study, most experiments involve the use of fraternal and identical pairs of twins reared together as well as fraternal and identical twin pairs reared apart. The percentage of the similarities between each member in a pair is called the concordance rate, and this number tends to be higher in identical twins than fraternal. However, when the trait in question being studied can vary dramatically, such as a persons aptitude, a different method is applied; in such a case, coefficient correlations are used.

The general intelligence quotient (IQ) correlation rate between fraternal twins reared together is .60, whilst the coefficient for identical twins reared together is .86.  Meanwhile, the correlation for identical twins reared apart is .77. I can relate to this statement because sister and I, who were reared together and are identical have very similar grades and tend to excel in similar subject areas. This points to the idea that although a person's intelligence is dependent on their education, their capacity to understand relies on their genetic makeup. The fact that identical twin pairs always have higher correlations than fraternal twins, even when they are reared apart, is a clear affirmation that nature dominates over nurture in this area.

Although there isn't a standard definition of intelligence, it is accepted that identical twins have rates of concordance than fraternal twins, showcasing that a person's genes correlates with their ability to perceive.

Sigelman, C. K., & Rider, E. A. (2009). Life-span human development [ed. VI, pp. 74-79]. Retrieved from http://books.google.com/books?id=Nn8tgkPSKB4C&printsec=copyright#v=onepage&q&f=false

 Joseph, J. (2004). The gene illusion: genetic research in psychiatry and psychology under the microscope [pp. 308-311]. Retrieved from http://books.google.com/books?id=OyDQlKwRpfwC&printsec=copyright#v=onepage&q&f=false

Sexual Orientation Affected by Genes

Though it is widely known that our make-up is formed by both our upbringing and our environment, many still argue about which of these factors affect sexual orientation. One of the ways that scientists have tried to tackle this question is by studying twins. An example of such are identical twins Alex and Mark Farley. Their mother, Jenny, left their father for another woman, which shows their mother was either homosexual or bisexual.

Both twins eventually came out as homosexual, with Alex coming out in the sixth grade, and his brother some time after that. Because of their violent relationship with their father, they began mingling with druggies and partaking in derogatory affairs. Due to this they were sent to rehab and separate boarding schools for two years. Eventually, Alex became dressing and acting as a woman, changed his name to Clair, and had surgery for a sex-change. Mark claimed that he had gone through puberty "with another person who has a body that's a lot like yours." He stated "I definitely found myself attracted to men from an early age. I knew that largely because Clair and I had such a close relationship." Clair stated she tried creating "an identity that wasn't connected to Mark."

As can be seen with the situation between Clair/Alex and Mark as well as many other cases of twins, a person's sexual orientation is a trait that can be passed on through one's genes. Just as their mother Jenny was homosexual, both of her twins turned out to be gay as well and had to find ways to cope with this.

Once again, nature seems to dominate over nurture when it comes to a person's makeup.

Winn, Steven. (2007, June 16). Pair's tough teen years, one brother's sex change. San Fransico Chronicle, Retrieved from http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/06/16/TWINS.TMP&ao=2

Nature vs. Nurture

Based on the fact that Marina and I are a monozygotic pair reared together (MZT), you would expect us to have identical personalities to the core. However, we happen to have many differences- while she is artistic, I can barely draw a stick-person. And whereas she has a knack of eating salty foods, everyone that knows me well can quickly say that I have the strongest sweet tooth out there. Nevertheless, we unquestionably share striking similarities as well. For one thing, we're both sporty (we've both participated in gymnastics, soccer, volleyball, swimming etc.), love shopping, are studious in school, and have a passion for traveling. Let it be said, I have often wondered what evoked our differences, since we are genetically identical and grew up in the same environment.

However, Marina, being my twin, understands me in ways other people don't. Although many friends that are close claim to be able to finish each others' sentences, my sister and I have an even deeper, freakish connection that our friends jokingly call our "twin telepathy."

L. Wright, who is mentioned in an journal about the renowned Minissota Study of Twins Reared Apart, says that "the science of behavioral genetics, largely through twin studies, has made a persuasive case that much of our identity is stamped on us from conception." This study, commonly known as MISTRA, addressed behavioral and personality differences and similarities between twins who were separated at birth and were met up years later. According to the article, monozygotic, or identical twins reared apart (MZA) had higher rates of personality correspondences than dizygotic, or fraternal twins reared apart (DZA). This points to the idea that genetics are truly a blueprint of our personalities.

Many cases show that the environment and social status of twins affect their personality, as seen in the case of  Mildred and Ruth, two fifteen year old MZAs. Ruth had grown up in a poor family that wasn't social, while Mildred wasn't brought up in a poor family and has "always been encouraged to make friends..." Psychologists claim that Ruth's unsocial, lonely upbringing may have led to her mindset of inferiority, while Mildred had a more "confident and more or less expansive" aura.

Therefore, it is my understanding that although the environment a person grows up in plays a key role in their personality, it doesn't makeup who they are and what they will be like, but rather influences the personality that has already been given to them in their genes.

The idea that our personalities may have been handed to us from the moment of our birth, only to be somewhat influenced by our upbringing is mind-boggling. This field of psychology is still fuzzy to scientists, and though they progress in their research and expand their knowledge on the subject, their findings continue to confound them. As L. Wright puts it, "The field of psychology has been shaken by separated-twin studies."

 Joseph, J. (2008). Separated twins and the genetics of personality differences: a critique. The American Journal of Psychology, 114(1), Retrieved from http://jayjoseph.net/yahoo_site_admin/assets/docs/AJP_MISTRA_PDF.157214425.pdf

Genetic Blueprint Plays a Roll

In my quest to learn more about studies concerning twins, my sister was kind enough to lend me her book Psychology Seventh Edition, by David G. Myers. I have found that there have been many striking instances where twins who were reared apart at birth, unknown about the existence of their counterpart, met up again and lived lives with daunting similarities.

An example of such are twins Jim Lewis and Jim Springer. These identical twin brothers were separated thirty-seven days after the day of their birth, and for 38 years lived unaware about having a brother. When Springer learned about his sibling, he set out to find him, only to find that like him, his twin brother who was coincidentally also named Jim had undergone a vasectomy, had a hobby of working in his wood shop, watched stock-car racing, and had a dog named Toy. Additionally, both commonly suffered from mid-day migranes, and Lewis named his son James Alan, while Springer named his James Allan.

This bizzare tale about identical twins reared apart is not the first of its kind, and it leads to the question as Myers puts it, "How much are our differences shaped by our differing genetic blueprints? To what extent are we formed by our upbringing...culture... and by our current circumstances?"

Myers, D. G. (2004). Behavior genetics: predicting individual differences. Psychology (pp. 108-110). New York, NY, USA: Worth Publishers.

A Relatable Topic

Originally, I had much too many ideas on topics to blog about, and since I knew that I wanted to take a scientific approach towards my essential question, all the topics I was interested in were relating to this branch. My other ideas were exceptionally broad, and being undecisive as I am, I couldn't come to a decision on what to dimish them to. Thus, I resorted to tackling my curiosity regarding what twin studies have revealed about the environmental vs. genetic effects on people.

The primary reason why I chose this topic to begin with has to do with being a twin myself. In being so, I can connect with the studies that I will endeavor in and relate to them on a personal account. However, a major portion of my interest in this topic comes from the psychology behind it. Therefore, my principal reasons for deciding to study this subject come from a relation on a personal account entwined with an interest in the science behind the topic.

Having a seemingly identical counterpart, I have a natural curiosity on the matter, and have for a long time desired to extend my limited knowledge on the subject. I hope that my findings guide me towards an even greater respect for psychology.

Me and my twin sister, Marina